After building the class files,
it's common to collect them into
a Java archive (.jar) file,
which you do by calling the Jar Builder method.
If you want to just collect all of the
class files within a subdirectory,
you can just specify that subdirectory
as the Jar source:

If you want to keep all of the
.class files
for multiple programs in one location,
and only archive some of them in
each .jar file,
you can pass the Jar builder a
list of files as its source.
It's extremely simple to create multiple
.jar files this way,
using the lists of target class files created
by calls to the Java builder
as sources to the various Jar calls: